Changeset struct undefined

Hello everbody. I’m just getting started learning Phoenix and I’m trying to create a basic Github clone as a learning project. I got stuck on an issue regarding the changeset struct, and couldn’t fix my problem with some googling.

Problem

I’m following this tutorial to create the file uploading system. I’ve added one additional field (see the migration below), other than that I followed the tutorial pretty closely. I’m currently at the step where he is testing his module using the changeset function in IEX. I’ve tried the following in IEX:

iex -S mix
alias Gutter.Gits.Upload
%Upload{}

and get the following error:

Gutter.Gits.Upload.__struct__/1 is undefined, cannot expand struct Gutter.Gits.Upload. Make sure the struct name is correct. If the struct name exists and is correct but it still cannot be found, you likely have cyclic module usage in your code

This is my Gutter.Gits.Upload module, stored in a file named upload.ex

defmodule Gutter.Gits.Upload do
  use Ecto.Schema
  import Ecto.Changeset

  schema "uploads" do
    field :size, :integer
    field :filename, :string
    field :hash, :string
    field :user_id, :string

    timestamps()
  end

  @doc false
  def changeset(upload, attrs) do
    upload
    |> cast(attrs, [:filename, :size, :hash, :user_id])
    |> validate_required([:filename, :size, :hash, :user_id])
    |> validate_number(:size, greater_than: 0)
    |> validate_length(:hash, is: 64)
    |> unique_constraint(:filename)
  end
end

The migration used to create the module:

defmodule Gutter.Repo.Migrations.CreateUploads do
  use Ecto.Migration

  def change do
    create table(:uploads) do
      add :filename, :string
      add :size, :bigint
      add :hash, :string, size: 64
      add :user_id, references(:users, on_delete: :delete_all), null: false

      timestamps()
    end
    create index(:uploads, [:hash])
  end
end

I feel that the error is pretty simple but can’t figure out what it is. From what I understand the struct name is correct, and I don’t think that I have any cyclical module usage since my program mostly contains generated code. Thanks for reading